Access to clean water is an issue for almost half of the Earth’s 7 billion strong population. According to the World Health Organization, only 59% of the population have access to clean water through household connections (that is through running water sources on their personal property). Specifically, only 16% of people in sub-Saharan Africa have access to clean water. While many towns may have access to constructed wells, due to financial and labour constraints these wells are often poorly maintained and contain contaminated water.

Access to unclean water is a huge issue for these communities as the contaminated water can cause huge breakouts of Diarrheal illnesses and cholera, which often spread quickly in the small villages. Even the long distances villagers often have to walk to sources of clean water can be harmful as it often takes a great length of time that could be better spent in income earning labour or education for children.

Water plays an essential role in the body, if you didn’t know already. It plays a huge role in body temperature control, mainly through sweat which can be incredibly important  in Africa where average summer temperatures can reach up to 34 degrees Celsius. Furthermore, it is the main component of blood plasma which provides blood with its fluidity. If water is lacking blood flow will slow as will the transport of essential substances for growth such as nutrients. This results in widespread malnutrition within the African population. Also, without water, possibly harmful bodily waste products will build up in the kidneys and can result in terrible illness.

It is for this reason that our group has decided to aim to create a cheap, easy to construct basic water filter, that will be able to effectively clean and purify dirty contaminated water into a form safe for drinking. This will allow these villages to easily filter any unclean surface water or water from poorly kept wells, and maintain hydrated, greatening their odds of escaping the poverty cycle.

Thought Process:

-Prior Planning:

We knew that we wanted to make the water filtration process more efficient so we conceived the idea of using centrifugal force as a solution. Our initial idea was a three chambered cylinder that could be sealed for transportation and use.

Through thorough online research, we discovered the necessary ingredients for designing this device. All the devices we found had the following ingredients in common:

  • Activated Charcoal
  • Dirt
  • Sand
  • Gravel
  • Small Rocks

As an extension of this, a few designs had different forms of physical filters such as fabric or filter paper. For this reason we deemed the purchase of filter paper important to fully filter the water. We discussed this and decided lab quality filter paper wouldn’t be accessible for the audience we intended it for so Coffee paper was chosen as a substitute.

In researching we found that iodine could be used to kill the remaining bacteria in the water, however, the iodine left in the water is detrimental for a person’s health. In continued research we found filtering this iodine diluted water through activated charcoal we could further purify the water to a drinkable quality.

Leo went out the day prior to the start of the Group 4 project and collected the necessary materials:


Recycled Materials:

  • 3x 1.5ltr bottles
  • 1 kg of Sand
  • 1 kg of Gravel
  • 1 kg of Dirt


  • 2 Roll of Duct tape - $5
  • 2 bag of cotton wool buds - $6.60
  • Coffee Filter Paper - $2.15

Total Cost:



On the first day we began by discussing how best to layer the filtration device. We concluded that we should layer it from coarse to fine (beginning with gravel and working down to sand - ending in filter paper). We ran into an issue on this first attempt as no water would filter through at all. Following consultation we discovered that in order for the water to flow, the cap need be removed as while the cap was on that air pressure within the lower chamber kept the water from falling through to the second chamber. While this allowed some droplets to flow we still struggled to get large quantities of water out and eventually it ceased to flow once again.


 Image Above: Initial prototype design

This realisation caused the group to abandon the group's original idea of a portable, swingable water filter. Once we realised that ease and portability were impossible to achieve, a new priority was decided, and that was achieving maximum water purity.

We took apart our model and found the large clump of cotton wool buds to be doing little for the filtration and forming clumps the water couldn’t pass. In removing this and remaking the filter we had further problems with the water coming out yellow.

We realised quickly dirt/ soil carry with it a multitude of bacteria and is incredibly insanitary. To fix this we had to abandon our use of soil and switch our primary filter to sand. From here we finally started to produce some colourless liquid however we had no means of testing its purity and were down one day of work.

-Day 2

Following the failures of the previous day, we decided to really gun it hard overnight, and we came up with a number of complex plans with a much higher chance of success. Evaluating each of these online, we decided on one method that would be accessible and easy to do while still maintaining a high quality of water. This was what we eventually used, and will be discussed in the final design section. We decided on a two stage water filtration process that used the initial sand and gravel filter as well as a solar still to guarantee maximum water purity.

We simplified our original idea, deciding to instead stripping back the concept and using only two layers of sand separated by a layer of gravel. Despite its simplicity the results were great. We also took greater care in the utilisation of sand. On Day 1 we simply sifted the sand to remove any large molecules, today we washed it instead, which I believe greatly helped the results of the filter.

Following the new and improved sand and gravel filter we installed a solar still on the roof. The aim of this solar still is to filter out any remaining microscopic bacteria left in the water and provide only pure drinkable water. The solar still was a late addition but as the day went on it proved to be extremely effective at filtering the water.

Another plan we had had was to put iodine tablets in the water after the initial stage of filtering to remove impurities. However this would have the consequence of making the water even more unsafe to drink due to the reactions iodine could have in the system. Therefore the iodine mix was fed through a filter of two layers of filter paper with a layer of activated charcoal in between. This new filter, while slow, effectively removed the iodine from the water and provided another method for purifying the water. We decided this was an ineffective solution for our target audience as they would not have access to these iodine tablets.


Photo Above: Left solution - Iodine mix before filtration Right Solution - Iodine mix after filtration

Dissolved O2(mg/L)

Nitrate/ nitrite


Tap water


0ppm both


Before filtration


Nitrate 10ppm


Post filtration


0ppm both


Final Design:

The Final Design is a two step system that can completely clean and filter the water of bacteria:

Initially, the water is run through a layer of sand, then gravel and then another layer of sand. This works to filter out larger and smaller particles within the water thus making the visibly pure. Gravity’s effect on the water pulls it through the filter, while the combination of small, then large then smaller particles thoroughly filters the water passing through.This water then passes through a small bud of cotton wool and a sheet of coffee filter paper to filter any remaining particles in the water. The results can be seen below

5.pdf 4.pdf  

Photo on the left: left sample is filtered water, right sample is tap water

Photo on the Right: Initial stage of water filtration

The filtration process

The iodine was successfully dissolved in the water, indicated by its change in colour. In addition, to test it, we put starch into it. The solution turned a very dark purple, indicating a very strong iodine presence. Then we filtered the iodinated solution through two layers of coffee grade filter paper with activated carbon in between. The activated carbon clung to the iodine and removed it from the water. The final layers of filter paper were to remove any large particles of the activated carbon. The filtered final solution was then also subjected to the starch test - the test turned negative for major traces of iodine. There was virtually no purple hue, and this is evidenced very clearly in the following photo. Hence, we managed to kill the bacteria with the iodine, and finally managed to remove the iodine from the final, 100% potable water. The final water tasted somewhat of iodine, but our subjects survived the next 5 hours, so we can finally verify that the water was drinkable.

Solar still update

The solar still was checked on at 11:15 a.m. The results are shown in the picture below:

The temperature on the roof was very hot, and made it easier to evaporate the water. This was emphasised by the solar oven made by another group - they reached over 100 degrees celsius. The temperature on the ground was 27 degrees, and about 3-5 degrees hotter on the roof. Accentuated by the implementation of a parabolically shaped reflective device, we managed to further focus the sunlight rays into the water in the tray. Increasing the temperature of the water by doing this made it evaporate faster, and hence condense more on the clingwrap. This proved a clean source of potable water that could be produced very cheaply.

By the end of day 2 the design had completely changed from the start of the project. The device was now comprised of two stages and focused primarily on maximum filtration rather than efficiency

After this design, the water that has been filtered is fed into a solar still where it is slowly evaporated by the sunlight. The evaporated water molecules condensate onto the cling film over the top of the solar still. Rocks placed above the clingfilm cause the water to run towards and drip into a container. Due to the condensation reaction of the water in the solar still, any remaining bacteria is removed and the final product is pure, drinkable water. This process would work much more efficiently in the hotter climates of Africa.


Image left: Solar Still evaporating water on the roof of the school.